The present invention generally relates to subsurface valves. More particularly, the present invention relates to an apparatus and method to operate a subsurface valve with a capillary tube extending from a surface station. More particularly still, the present invention relates to an apparatus and method to operate a subsurface valve with a capillary tube extending from a surface station from within the tubing string upon which the valve is mounted. The valve may be a safety valve, a storm check valve, or a choke valve. The flow interrupting device or valve may be formed from a flapper, a ball valve, or a gate valve or any other type of flow diverting valve assembly which may be actuated from the surface.
Subsurface valves are typically installed in strings of tubing deployed to subterranean wellbores to prevent the escape of fluids from one production zone to another, including the surface. The application of the present invention relates to all types of valves, but for the purposes of this disclosure the illustrative application shall be safety valves used to shut in a well in the absence of continued hydraulic pressure from the surface. This limitation on the scope of this disclosure should not be used to limit the scope of the disclosure for non-safety valve applications which may be readily apparent from the disclosure made herein to a person having ordinary skill in this art.
Absent safety valves, sudden increases in downhole pressure can lead to catastrophic blowouts of production and other fluids into the atmosphere. For this reason, drilling and production regulations throughout the world require safety valves be in place within strings of production tubing before certain operations can be performed.
One popular type of safety valve is known as a flapper valve. Flapper valves typically include a closure member generally in the form of a circular or curved disc that engages a corresponding valve seat to isolate one or more zones in the subsurface well. The flapper disc is preferably constructed such that the flow through the flapper valve seat is as unrestricted as possible. Usually, flapper-type safety valves are located within the production tubing and isolate one or more production zones from the atmosphere or upper portions of the wellbore or production tubing. Optimally, flapper valves function as large clearance check valves, in that they allow substantially unrestricted flow therethrough when opened and completely seal off flow in one direction when closed. Particularly, production tubing safety valves prevent fluids from production zones from flowing up the production tubing when closed but still allow for the flow of fluids (and movement of tools) into the production zone from above.
Flapper valve disks are often energized with a biasing member (spring, hydraulic cylinder, etc.) such that in a condition with zero flow and with no actuating force applied, the valve remains closed. In this closed position, any build-up of pressure from the production zone below will thrust the flapper disc against the valve seat and act to strengthen any seal therebetween. During use, flapper valves are opened by various methods to allow the free flow and travel of production fluids and tools therethrough. Flapper valves may be kept open through hydraulic, electrical, or mechanical energy during the production process.
Examples of subsurface safety valves can be found in U.S. Provisional Patent Application Ser. No. 60/522,360 filed Sep. 20, 2004 by Jeffrey Bolding titled “Downhole Safety Apparatus and Method;” U.S. Provisional Patent Application Ser. No. 60/522,500 filed Oct. 7, 2004 by David R. Smith and Jeffrey Bolding titled “Downhole Safety Valve Apparatus and Method;” U.S. Provisional Patent Application Ser. No. 60/522,499 filed Oct. 7, 2004 by David R. Smith and Jeffrey Bolding titled “Downhole Safety Valve Interface Apparatus and Method;” all hereby incorporated herein by reference.
This application further incorporates by reference U.S. Non-Provisional application Ser. No. 10/708,338 Filed Feb. 25, 2004, titled “Method and Apparatus to Complete a Well Having Tubing Inserted Through a Valve” and U.S. Provisional Application Ser. No. 60/319,972 Filed Feb. 25, 2003 titled “Method and Apparatus to Complete a Well Having Tubing Inserted Through a Valve”.
One popular means to counteract the closing force of the biasing member and any production flow therethrough involves the use of a capillary tube to operate the safety valve flapper through hydraulic pressure. Traditionally, production tubing having a subsurface safety valve mounted thereto is disposed down a wellbore to a depth of investigation. In this circumstance, the capillary tubing used to open and shut the subsurface safety valve is deployed in the annulus formed between the outer profile of the production tubing and the inner wall of the borehole or casing. A fitting outside of the subsurface safety valve connects to the capillary tubing and allows pressure in the capillary to operate the flapper of the safety valve.
Furthermore, because former systems were run with the production tubing, installations after the placement of production tubing in the wellbore are invasive. To accomplish this, the production tubing must be retrieved, the safety valve installed, the capillary tubing attached, and the production tubing, safety valve, and capillary tubing run back into the hole. This process is expensive and time consuming, so it is typically performed on wells having enough long-term production capability to justify the expense.